How is sex determined in human beings ?

Explanation

In humans out of 23 pairs of chromosomes present 22 pairs are exactly same in both males and females known as autosomes.
= The 23rd pair of chromosome is the sex chromosome i.e. a pair of X-chromosome (XX) is present in females and males having one X and Y chromosome (XY).
= During spermatogenesis, in case of male, two types of gametes are produced
= The 50% of total sperms produced carry X-chromosomes and the rest 50% carry Y-chromosomes besides autosomes.
= Female produces only one type of ovum with an X-chromosome.
= If an ovum fertilises with a sperm carrying Xchromosome the zygote develops into female [XX) and if an ovum is fertilised with sperm carrying Y-chromosome zygote thus formed will be male XY.

= Hence, the genetic make up of sperm, which fertilises the ovum determines the sex of a child.
= These are 50% chances of having either a male or female in each pregnancy.